Figure 1

Regions in the $m_{\varphi }-g_{\varphi }$ plane that are ruled out by either Planck measurements of the CMB or searches for time-varying signals in the solar neutrino data of Super-K and SNO. We also show the projected reach of the LENA liquid scintillator neutrino experiment. On the top axis, for each value of $m_{\varphi }$ we display the corresponding period (in days) of the modulation imprinted on the solar neutrino flux ${\tau }_{\varphi }\equiv 2\pi /m_{\varphi }$. In the gray shaded region, dark matter lighter than $\sim {10}^{-21}\mathrm{eV}$ is in slight tension with observations of the Lyman-$\alpha$ forest. Current searches for anomalous periodicities in the solar neutrino data can probe DM-neutrino couplings that are orders of magnitude below limits derived from cosmological observations.